I have installed push.js but it still don't run on node.js backend

[kuspia]

const express = require('express');
const app = express();
const Push = require('push.js')
app.use(express.json());
app.get('/', (req, res) => {   
res.sendFile(__dirname + '/index.html');
});
app.post('/', async (req, res) => {
var f = 0 ;
// I get values here from the frontend's form and process them and do calculations to update f
if(f>10)
{
Push.create("Hello nice" );
}
else
{
Push.create("POOOOOOOOOOR man try again" );
}
});
app.listen(3000);

I installed push.js as a npm module but I don't understand after my server is started and rendered index.html, I see the following as an error:

Please try to understand why I want to do so, in my backend I fetch a value from the frontend's form and then process it and if it is in the range I need to send a push notification somehow to the frontend user which I am failing to do so because of the above error.

I am able to send a notification by making a notify button on the frontend and if the user press it, as I included the .js files in my HTML and things work fine, but I just don't understand what is the use of npm install push.js if a node.js backend is unable to send the notification to frontend when desired.

[thiagolmoraes]

Same problem!

[matronator]

The error states: navigator is not defined, which makes sense as navigator is only available in browsers and not in node. I think this library is for browser only. You need to call the Push methods on the frontend.

[xbsheng]

This is the npm library used in front-end web pages and cannot be used in nodejs